As you may see, the error comes from the server. As it turns out, desktop client logs won't give any real clues on what is going on on the server when these internal errors occur. Since you are running an old version, your first next step would be to upgrade your server to the latest 8.1.1 version.

The latest official release versions of Acronis Files Advanced are available here. All server installer downloads will require confirmation of ownership with your serial number. Upgrade instructions can be found here.

If the issue still persists, feel free to create a support ticket on our web-site. We will need to review the server logs then.